Device to control speed and torque of line return in spring drive device

ABSTRACT

A governing device including a return spring and a spool upon which a line or cord is wound, includes on a fixed housing element a magnetic or a conductive material and on the rotating portion of the spool respectively either a magnet or a layer of conductive material is provided. When the line or cord is retracted by the spring, a hysteresis loop is formed in the conductive material by the magnet causing an eddy current which slows down the rate of retraction of the line to provide safety in the rate of return of the line or cord.

I FIELD OF THE INVENTION

[0001] This invention relates to a power spring driven retractable lineor cord device having eddy current governor control of line or cordreturn for safety.

II BACKGROUND OF THE INVENTION

[0002] In U.S. Pat. 5,920,997 granted Jul. 13, 1999 an automaticallyretractable chalk line device is disclosed including a power spring 30which engages a gear 44 which in turn is in driving engagement with aspool 90 which winds a chalk line 100 having a chalk line end portion106.

[0003] While this chalk line device operates very satisfactorily, aproblem has occurred concerning the retraction of the chalk line device.The power spring 30 generates such a large force that the chalk line 100is in some circumstances retracted so rapidly as to cause danger to theoperator during the retraction operation.

[0004] U.S. Pat. No. 4,116,397 discloses a drive arrangement for yarnstorage and dispensing units including a winding member 1 rotablymounted on a fixed shaft 3 by a bearing 2. Winding member 1 comprisesthe rotor of a drive motor, and its inner wall carries a steel spring 13having permanent magnetic or hysteresis characteristics. This hysteresisring rotates about a laminar stator core 14 which carries the motor coil15. In this patent in order to prevent deviations from the idealcharacteristic of a hysteresis motor from influencing the length of theyarn coil wound upon the winding member of the yarn storage anddispensing unit, the hysteresis motor used according to the inventionfor driving the storage and dispensing unit is provided with means forsuppressing eddy currents. This eddy currents suppression comprises ahysteresis ring, the axial width of which is restricted to the axiallength of the laminated stator core of the motor. This reduces the eddycurrents.

[0005] In accordance with the present invention, the eddy currentfeature is used to control the speed of retraction of a line or cord tomaintain the return speed of the line or cord within safe limits. Thusthe teachings of the '397 are in opposite to the present invention ofutilizing eddy currents to control the rate of retraction of the device.

[0006] U.S. Pat. No. 4,602,360 is directed to sound production deviceswith magnetic governors for use in toys. The governor mechanism 40includes rotors 42 and 44 and first and second magnets 46 and 48. Thereturn force of spring 20 urges rotor 42 in a counterclockwise directionas viewed in FIG. 5, at which point elements 42B and 42C are in thedotted positions in radial alignment with the sub-openings 56A and 56Cand rotors 42 and 44 then turn in unison causing the magnets 46 and 48to slide radially outwardly with sub-openings 56A and 58A slidingoutward in engagement with elements 42B and 42C until friction pads 50and 52 come in contact with the inner perifery of housing portion 11Bcausing a braking action to regulate the speed of the mechanism. Howeverthere is no involvement of eddy currents as called for in the presentinvention to effect the return control mechanism. Thus U.S. Pat. No.4,602,360 acts on a different principle in effecting its braking action.

[0007] In U.S. Pat. No. 4,779,814 granted Oct. 25, 1988, a backlashprevention device for a fishing reel is provided wherein a spool isconnected to a non-magnetic electroconductive member associated withbreak magnets that generate eddy currents in the non-magneticelectroconductive member to provide a breaking force on the spool. Thebacklash prevention device includes movable magnets for varying thebreaking force to provide a breaking force on the spool. However, thispatent is not directed to a spring drive system.

III SUMMARY OF THE INVENTION

[0008] A. Objects

[0009] The terms “line” or “cord” as used herein are to be construed asa string, cord, ribbon, band or similar mechanical element capable ofbeing wound around a spool, drum or similar device.

[0010] One object of the present invention is to provide an arrangementfor governing the speed of a spring drive line or cord retractiondevice.

[0011] Another object of the present invention is to utilize the eddycurrent principle in governing rotational velocity and torque in a sringdrive device.

[0012] Another object of the present invention is to utilize the eddycurrent principle in governing the speed of retraction in a spring drivedevice.

[0013] Another object of the present invention is to provide anarrangement for governing the speed of the return of the a line or cordactivated by a spring motor after the line or cord has been extended toeffect a measurement.

[0014] Another object of the present invention is to utilize the eddycurrent principle in achieving the control of the rate of retraction ofa chalk line device.

[0015] In accordance with the present invention, a governing deviceincluding a return spring and a spool upon which a line or cord iswound, includes on a fixed housing a magnetic or a conductive materialis provided and on the rotating portion of the spool respectively eithera layer of conductive material or a magnet is provided. When the line orcord is retracted by the spring, a hysteresis loop is formed in theconductive material by the magnet causing an eddy current which providesa force opposite to the angular motion which slows down the rate ofretraction of the line or cord to provide safety in the rate of returnof the line or cord.

IV. THE DRAWINGS

[0016]FIG. 1 is an exploded perspective view of an automaticallyretractable chalk line device in U.S. Pat. No. 5,920,997.

[0017]FIG. 2 is a schematic perspective view of the external housing ofthe chalk line device shown in FIG. 1.

[0018]FIG. 3 is a horizontal sectional view looking in the direction ofthe arrows along line 3-3 in FIG. 2.

[0019]FIG. 4 is a vertical sectional view looking in the direction ofthe arrows along line 4-4 in FIG. 2.

[0020]FIG. 5A is a partial vertical sectional view illustrating thebrake activating mechanism with the brake in the activated position.

[0021]FIG. 5B is a view similar to FIG. 5A with the brake in thedeactivated position.

[0022]FIG. 6A is partial horizontal sectional view illustrating themovable plate to allow insertion of chalk into the assembly.

[0023]FIG. 6B is a vertical sectional view looking in the direction ofthe arrows along the line 68-68 in FIG. 6A illustrating details of themovable plate assembly.

[0024]FIG. 7 is a horizontal sectional view looking in the direction ofthe arrows along the line 7-7 in FIG. 8.

[0025]FIG. 8 is a vertical sectional view looking in the direction ofthe arrows along the line 4-4 in FIG. 2, with the chalk line removed.

[0026]FIG. 9 is a horizontal sectional view looking in the direction ofthe arrows along the line 9-9 in FIG. 11.

[0027]FIG. 10 is a sectional view looking in the direction of the arrowsalong the line 10-10 in FIG. 9.

[0028]FIG. 11 is a sectional view looking in the direction of the arrowsalong the line 11-11 in FIG. 12.

[0029]FIG. 12 is a sectional view looking in the direction of the arrowsalong the line 12-12 in FIG. 11

[0030]FIG. 13A is a sectional view looking in the direction of thearrows along line 13-13 in FIG. 14.

[0031]FIG. 13B is a sectional view looking in the direction of thearrows along the line 13-13 in FIG. 14.

[0032]FIG. 13C is a sectional view looking in the direction of thearrows along the line 13-13 in FIG. 14.

[0033]FIG. 14 is a sectional view looking in the direction of the arrowsalong line 14-14 in FIGS. 13A and 13B.

V. DESCRIPTION OF PREFERRED EMBODIMENTS

[0034] The automatically retractable chalk line device of U.S. Pat. No.5,920,997 is indicated in the drawings generally at 1. The assemblyincludes a housing 2, including a housing body portion 3, having a topsurface 4, and a vertical wall 5. The housing includes a springenclosure portion 6, including an arcuate member 7, a bottom plate 8,including vertical portions 9 and 10 is integral with the arcuateportion 7 by means of fasteners or integral molding.

[0035] The housing includes a top assembly 10, including a top member11, having downwardly extending sides 12. A spool retainer portion 14,includes an extension of body portion 3 indicated at 16, a bottom plate18, which supports the spool including shoulder 20. Mechanical fasteners22 hold the assembly together through openings 23, illustrated in FIG.3.

[0036] A chalk line discharge portion 24 includes downwardly andinwardly extending walls 26 and 28 terminating in a vertical wall 29,having an opening 29 a through which the chalk line exits.

[0037] A power spring 30 includes a plurality of coils 32 and a housingbody portion 3 includes a coil retainer 33. The spring includes an innerend 34 which engages a spring shaft, 36 which extends vertically throughthe spring 30 and engages a first gear assembly indicated generally at40. A spring support plate 37 a spring cover 38 are located between thespring and the gear assembly 40 (FIG. 1).

[0038] The gear assembly 40 includes a large gear, 41 having teeth 42,which engage a small gear 43, having teeth 44 (FIG. 1). Shaft 36mechanically engages large gear 41 through non-round projection, 39 onthe shaft and non-round opening 45 on the large gear. Bottom plate 8holds the gear assembly in place. The difference in diameter betweenlarge gear 41 and small gear 43 provides a substantial mechanicaladvantage.

[0039] Small gear 43 includes a non-round opening 46 which receives ashaft 50, having a non-round end portion 51. Vertical shaft 50 includesa nonround upper end portion 53, which engages a non-round opening 61,in gear assembly 60. Non-round opening 61 is located within a large gear63 which has teeth 65 which engages small gear 64 having teeth 67.

[0040] A brake assembly 70 is provided including a brake pad 72 which inengaged position engages the large gear surface 68 and in disengagedposition is spaced therefrom as illustrated in FIGS. 1 and 5B. The brakepad 72 is integrally connected to top cover 11 and is nonmoveable. Gearassembly 60 is provided with limited vertical movement on shaft 50 toprovide the relative movement between brake pad 72 and gear 63.

[0041] A brake activating assembly 73 includes a horizontally movableplate 74 which is movable over a cam surface 75 located on horizontalhousing surface 76. Plate 74 includes an opening 77 for passage of spoolshaft 92 to engage small gear 64. A pair of resilient springs 78 held inplace with rectangular wall housing 79 resiliently bias a release button80 into a position wherein button release projection 82 engages anopening 83 in plate 74 to maintain the plate 74 and the gear 63 in theengaged position with disc 72.

[0042] The spool assembly indicated generally at 90 includes a spoolshaft 92 extending upwardly from an upper plate 94. A spool core 95extends between upper plate 94 and bottom plate 96 to hold the chalkline in place. Upper plate 94 and bottom plate 96 are held in placeagainst formed shoulders 97 and 98. The chalk line 100 passes throughchalk line retainers 102 and 104 and housing opening 103, and includes aknot 105 an anchor 106 at its end.

[0043] The housing 2 includes an opening 110 as illustrated in FIG. 6Afor insertion of chalk.

[0044] A plate 112 is mounted for movement back and forth to open andclose this opening. The plate includes a projection 114 for moving theplate back and forth. The plate is also provided with another projection116 which engages a slot 118 in the housing to maintain the plate in theclosed position.

[0045] To open the housing to receive chalk the projection 114 isgrasped and sufficient force is provided to overcome the interferencefit with the projection 116 and the slot 118 and plate 112 is moved fromright to left in FIG. 6A. FIG. 5A shows the brake assembly 70 in thebrake engaged position in which the brake pad 72 is an engagement withthe surface 68 on the large gear 61. In this position the manual releasebutton 80 is in the position shown with the projection 82 located withinthe plate slot 83.

[0046] To release the brake, the manual release button 80 is rotatedwith the grip portion 85 in a clockwise direction against the bias ofthe spring 78. This forces the plate 74 from right to left so that theslot 77 is located upon the cam 75 and thereby allowing clearancebetween the brake pad 72 and the large gear surface 68.

[0047] In the operation of the automatic retractable chalk line device,to fill the device with chalk, the plate 112 is moved from right to leftin FIG. 6A and the chalk is then poured into the housing through opening110 so as it will engage the chalk line 100 as the chalk line exits thehousing. After filling the housing the plate is moved from left to rightin FIG. 6A until the projection 116 engages the slot 118 to hold theplate in the closed position. The anchor 106 is connected to a suitableanchor position in line with the chalk line to be prepared. The operatorthen moves from right to left in FIGS. 1 to 4 and in so doing the chalkline is rotated about the core 95 to extend the chalk line. In so doingpower coil spring 30 is tensioned.

[0048] When the chalk line has been removed sufficiently to draw theline for the distance desired, the line is snapped in a manner similarto engaging a string instrument and the chalk forms the desired line.

[0049] To retract the line, the manual release button 80 is pivoted in aclockwise direction by the operator engaging the grip portion 85 and theplate 74 moves from right to left in FIGS. 5A and 5B whereby the camsurface 75 is located within the slot 77 of the plate, providingclearance between the brake pad 72 and the large gear 61. The power coilspring 30 is then free to unwind within the housing. This results inshaft 36 driving large gear 41 and small gear 44. Small gear 44 in turndrives shaft 53 and large gear 61. Large gear 61 drives small gear 64.Small gear 64 in-turn drives the spool shaft 94, which causes the chalkline 100 to be rotated back into the loaded position.

[0050] As an example, the power coil spring has a diameter of 3 inches,and is {fraction (1/64)}th inch in thickness. Large gears 41 and 61conveniently have a diameter of 2 and {fraction (9/16)} inches and smallgears 44 and 64 conveniently have a diameter of {fraction (15/16)} inch.

[0051] In accordance with the present invention, as shown in FIGS.10-12, the rate of retraction of a line or cord is reduced by the eddycurrect speed governor 200. The governor includes a housing 210enclosing a power spring 230 and an arbor 232 extending into upper andlower housing portions 212 and 214. The spool assembly 240 has acylindrical body portion 242 and upper and lower flanges 244 and 246which retain line 250 in place. The line passes through a retainer 280during winding and unwinding. At least one mechanical fastener 290 holdsthe housing in the assembled position.

[0052] A magnet assembly 260 includes north and south portions 262 and264 which generate magnetic field lines 266 as shown in FIG. 10. Aconductive disc 270 made of conductive material including but notlimited to copper, aluminium, silver, gold, steel, platinum is bonded orattached to rotatable flange 246. As the spool rotates the magneticfield lines generate eddy currents in conductive disc 270 which act in adirection to oppose the winding power of spring 230, and the motion ofthe spool.

[0053] In FIGS. 13A and 13B the gear assembly 40 described hereinaboveis provided.

[0054] In FIG. 13A the spool assembly 240″ includes upper and lowermagnet assemblies 260 a, 260 b which generate magnetic fieldsrespectively in upper and lower conductive plates 270 a and 270 b tooppose rotation and slow down the rate of retraction.

[0055] In FIG. 13B the spool assembly 240″ includes only lower magnetassembly 260 c which generates magnetic fields in lower conductive plate270 c to oppose rotation and slow down the rate of retraction.

[0056] In FIG. 13C the spool assembly 240′″ includes two independentlower magnet assemblies, 260 d and 260 e with conductive plate 270 dlocated between. Conductive plate 270 d, having non-round opening, 271mechanically engages non-round projection, 290 of spool assembly 240′″.Magnet 260 d is bonded or attached to bottom plate 18 a. Magnet 260 e isbonded or attached to circular cap 280. Circular cap 280, havingretainer groove, 282 snaps into retainer lip 300 of bottom plate 18 a,allowing said circular cap 280 to rotate frictionally in relation tobottom plate 18 a. Thumb tabs 281, outside knurl or other method isprovide for a means of manually rotating circular cap 280.

[0057] Manual rotation of circular cap 280, containing magnet 260 e, inrelation to magnet 260 d, causes the magnetic poles 262 and 264, in FIG.10, of the opposing magnets, to align or misalign in relation with eachother. This alignment varies the strength of magnetic fields acting uponthe conductive plate 270 d, therefore varying the opposing force ofrotation and allowing for a manually adjustable slow down rate ofretraction.

[0058] The advantage of the present invention is apparent. The line orcord is fully retractable through the action of the power coil springand the retraction is much safer because the rate of retraction isslowed down to a safe speed by the eddy current producing assemblies240, 240′, 240″ and 240′″.

[0059] It will be apparent to those skilled in the art that these eddycurrent producing assemblies may be used to control and govern the rateof retraction of any line or cord which is to be wound upon a spoolassembly powered by a power spring.

What is claimed is:
 1. A retractable line or cord device comprising: arotatable spool having means for retaining a flexible line or cord; apower spring mounted in driving relationship to rotate said spool; atleast a portion of said spool comprising a conductive portion or aportion of magnetic material capable of generating magnetic field lines;and a fixed member located adjacent said spool; said fixed membercomprising at least a portion of magnetic material capable of generatingmagnetic field lines if the spool comprises said conductive portion andproduce eddy currents in said spool conductive portion; and if saidspool comprises a portion of magnetic material capable of generatingmagnetic field lines, said fixed member comprises a conductive portion.2. A retractable line or cord device according to claim 1 wherein saidportion of magnetic material capable of generating magnetic field linescomprises a magnet assembly including a plurality of north and southpole portions.
 3. A retractable line or cord device according to claim 2wherein said conductive material comprises at least one materialselected from copper, aluminium, silver, gold, steel and platinum.
 4. Aretractable line or cord device according to claim 3 wherein saidconductive material comprises a disc made of said conductive material 5.A retractable line or cord device according to claim 2 wherein saidspool includes a spool assembly comprising upper and lower magnetassemblies which generate magnetic fields respectively in upper andlower conductive plates located in said fixed member to oppose rotationand slow down the rate of retraction.
 6. A retractable line or corddevice according to claim 2 wherein said spool includes a spool assemblycomprising a lower magnet assembly which generates magnetic fields insaid lower conductive plate located in said fixed member to opposerotation and slow down the rate of retraction.
 7. A retractable line orcord device according to claim 2 wherein said spool includes a spoolassembly comprising of two lower magnet assemblies, which generate amagnetic field in said lower rotating conductive disc, located betweensaid magnet assemblies; and a manually adjustable rotational member,containing one of said magnets which allow radial alignment of saidmagnets, in relation to each other, that allow the generating ofvariable strength magnetic fields in said lower rotating conductive discto oppose rotation and variably slow down the rate of retraction.
 8. Aretractable line or cord device according to claim 2 wherein a gearassembly is in driving engagement with said coil spring, and said coilspring includes a first shaft vertically extending within said coilspring and engaging said gear assembly.
 9. A retractable line or corddevice according to claim 8 wherein said gear assembly includes a firstlarge gear; said large gear being in driving engagement with a smallgear.
 10. A retractable line or cord device according to claim 9 whereinsaid small gear being in driving engagement with a second verticallyextending shaft; said second shaft being in driving engagement with asecond large gear; said second large gear being in driving engagementwith a small gear, laterally spaced therefrom; said second small gearbeing in driving engagement with a vertically extending spool shaft;said spool shaft being integral with said spool; said spool having aline or cord wound about a spool core.
 11. A retractable line or corddevice according to claim 10 wherein said line or cord extends outwardlyfrom said spool and anchoring means are provided for anchoring said lineor cord located outside said retraction device housing.
 12. Aretractable line or cord device according to claim 10 wherein brakemeans are provided for maintaining said power spring in tensionposition; and means for releasing said brake means are provided to allowsaid power spring to drive said first gear, said second gear, said thirdgear, said fourth gear, and said spool to retract said line or cord. 13.A retractable line or cord device comprising: a rotatable spool havingmeans for retaining a flexible line or cord; a power spring mounted indriving relationship to rotate said spool; at least a portion of saidspool comprising a conductive portion and a fixed member locatedadjacent said spool; said fixed member comprising at least a portion ofmagnetic material capable of generating magnetic field lines in saidspool conductive portion and produce eddy currents in said spoolconductive portion.
 14. A retractable line or cord device according toclaim 13 wherein said portion of magnetic material capable of generatingmagnetic field lines comprises a magnet assembly including a pluralityof north and south pole portions.
 15. A retractable line or cord deviceaccording to claim 14 wherein said conductive material comprises a disc.16. A retractable line or cord device according to claim 14 wherein saidconductive material at least one material selected from copper,aluminium, silver, gold, steel and platinum.
 17. A retractable line orcord device comprising: a rotatable spool having means for retaining aflexible line or cord; a power spring mounted in driving relationship torotate said spool; at least a portion of said spool comprising a portionof magnetic material capable of generating magnetic field lines in anadjacent conductive portion; and a fixed member located adjacent saidspool; said fixed member comprising a conductive portion which duringrotation of said spool receives magnetic field lines from said magneticmaterial in said spool, and generates eddy currents in said conductivematerial.
 18. A retractable line or cord device according to claim 17wherein said portion of magnetic material capable of generating magneticfield lines comprises a magnet assembly including a plurality of northand south pole portions.
 19. A retractable line or cord device accordingto claim 17 wherein said conductive material comprises at least onematerial selected from copper, aluminium, silver, gold, steel andplatinum.
 20. A retractable line or cord device according to claim 19wherein said conductive material comprises a disc made of saidconductive material.